For example, the cam shaft used in internal-combustion engines, such as engine of a car, tends to be changed from the conventional cast iron camshaft to assembled camshafts for the purpose of getting the lighter weight.
Furthermore the method for manufacturing a cam by sintering to which post-processing (grinding etc.) of a cam circumference side (cam profile) become unnecessary is also proposed. The method presents to cut down the manufacturing cost of the assembled camshaft after assembling a cam and a shaft.
For example, the Japanese patent reference (JP H08-295904: reference1) is related to the manufacturing method of a cam which is used by process flow s (1)–(3) as follows, (1): compacting of the powder for use in sintering, (2): sintering after (1), (3): thermal refining after (2). The reference mentions that correcting for reverse of direction of distortion which is produced by (3) is processed after (2) and changing the target circumference form of a cam utilizing distortion occurred by thermal refining is achieved.
Moreover, the European patent reference (EP 0718473: reference2) is related to the manufacturing method of a cam, which manufactures the cam shaft for internal-combustion engines, by the processes of sintering and sintering forging. The reference mentions that manufacturing and correcting a cam provisionally by taking into consideration a form error and a size are processed and post-processing is not necessary by making it change by thermal deformation produced in the cases, such as sintering.
However, the manufacturing method of a cam mentioned in the reference1 needs at least 4 processes, which are “compacting”, “sintering”, “correction”, and “thermal refining”. Comparing with the conventional the manufacturing method of a cam, the conventional one needs 4 processes “compacting”, “sintering”, “thermal refining”, and “post-process (grinding)” and both manufacturing methods have to need the same number of processes.
The manufacturing method of a cam mentioned in the reference1 is not able to reduce cost of manufacturing substantially.
The manufacturing method of a cam mentioned in the reference2 needs to take into consideration of thermal deformation such as “sintering”, “thermal refining”, etc. The methods have problems that a design and manufacture of the metallic mold for molding or the metallic mold for correction and the taking into consideration of thermal deformation are difficult.